Strongly basic AEM is usually prepared by using copolymerization of styrene and divinyl benzene in presence of polyethylene (PE) for industrial uses. The preparation of AEM is a two-step process. First step is the chloromethylation of styrene part in the copolymer and second one is the quaternary amination of the CH2—Cl part of styrene block in the copolymer film. The preparation of an AEM through this process is complicated and costly, because in the chloromethylation process, the common-used chloromethylether (CME) is carcinogenic and is potentially harmful to human health. An alternative way to prepare AEM is the graft copolymerization of vinyl monomers, such as 4-vinylpyridine, 2-vinylpyridine and vinylbenzylchloride onto various polymer films using various grafting technologies, such as UV-induced, plasma and irradiation methods. Several efforts have been made to avoid the use of CME for preparing AEM.
Reference may be made to U.S. Pat. No. 4,923,611 wherein it describes the preparation of anion-exchange membrane from resin containing a high molecular weight compound having haloalkyl groups by treatment with ultraviolet radiation or ionizing radiation.
Reference may be made to U.S. Pat. No. 4,253,900 wherein it discloses the preparation of bipolar ion exchange membranes from polystyrene-divinylbenzene-polyolefin composition wherein the polystyrene content of the component strongly acidic cationic membrane.
Reference may be made to US20090281245A1 wherein it discloses the preparation of proton exchange fuel cell membranes from graft or block copolymers containing sulfonated side groups.
Reference may be made to U.S. Pat. No. 4,329,434A wherein it describes the preparation of fluorinated cation exchange membrane containing carboxylic acid groups and sulfonic acid groups, both in the form of a specific pendant structure.
Reference may be made to the article “The radiation-grafting of vinylbenzyl chloride onto poly(hexafluoropropylene-co-tetrafluoroethylene) films with subsequent conversion to alkaline anion exchange membranes: optimization of the experimental conditions and characterization” published in J. Membr. Sci. 218, 147, (2003) by Herman et al. This paper reported the preparation of AEM by grafting of vinylbenzylchloride on copolymer matrix followed by amination.
Reference may be made to the article “Radiation-initiated graft copolymerization of 4-vinylpyridine onto polyethylene and polytetrafluoroethylene films and anion exchange membranes there from” published in J. Appl. Polym. Sci. 1469, 64, (1997) by Kostov et al. The article describes the preparation of AEM by radiation-initiated graft copolymerization of 4-vinylpyridine onto low-density polyethylene and polytetrafluoroethylene films by γ-rays from 60Co source in nitrogen atmosphere followed by quaternization.
Reference may be made to another article “Graft copolymerization of acrylonitrile and its binary mixture with 4-vinylpyridine onto isotactic polypropylene powder by pre irradiation method” published in J. Appl. Polym. Sci. 1197, 56 (1995) by Kaur et al. The article describes the graft copolymerization of acrylonitrile and its binary mixture with 4-vinyl pyridine onto isotactic polypropylene powder in aqueous medium, using γ-rays as an initiator.
Reference may be made to another article “Anionic membranes obtained by radiation grafting of 4-vinylpyridine onto poly(vinyl chloride)” published in Radiat. Phys. Chem. 157, 26, (1985) by Dessouki el al. The paper reported the preparation of AEM by radiation grafting of 4-vinylpyridine onto polyvinylchloride followed by quaternization with methyl iodide.
Reference may be made to another article “Preparation and properties of anion exchange membranes having pyridinium or pyridinium derivatives as anion exchange groups” published in J. Polym. Sci. A 49, 36 (1998) by sata et al. The paper reported the preparation of AEM with pyridinium groups from a copolymer membrane composed of chloromethylstyrene and divinylbenzene, and pyridine and pyridine derivatives.
Reference may be made to another article “Fundamental studies of a new series of anion exchange membranes: membrane preparation and characterization” published in J. Memb. Sci. 159, 199, (2001) by Xu et al. This article reported the preparation of a new class of cross-linked AEM from linear engineering plastics poly(2,6-dimethyl-1,4-phenylene oxide) by conducting the processes of bromination and amination at both benzyl and aryl positions. This article described the preparation of AEM without the use of carcinogenic CME. The prepared AEMs were characterized in terms of ion exchange capacity, water content, membrane potential and transport number of membrane. The results show that the membrane properties are significantly affected by the bromination processes: benzyl-substitution will enhance the ion exchange capacity and water content, while the aryl-substitution will decrease the water content with approximately unchanged ion exchange capacity.
Reference may be made to another article “Cross-Linked Poly(vinyl alcohol)-Poly(acrylonitrile-co-2-dimethylamino ethylmethacrylate) Based Anion-Exchange Membranes in Aqueous Media” published in J. Phy. Chem. B 198, 114, (2010) by Mahendra Kumar et al. This paper reported the preparation of AEM based on poly(vinyl alcohol) and copolymers of PAN and PDMA in aqueous medium. AEM prepared through this technique avoids the use of CME.
Reference may be made to another article “Novel anion exchange membrane based on copolymer of methyl methacrylate, vinylbenzyl chloride and ethyl acrylate for alkaline fuel cells” published in J. Memb. Sci. 206, 354, (2010) by Xu et al. This paper reported the preparation of AEM based on the copolymer of methyl methacrylate, vinylbenzyl chloride and ethyl acrylate for the potential applications for direct methanol alkaline fuel cell.
Reference may be made to another article “Protonation and diffusion phenomena in poly(4-vinyl pyridine) based weak anion exchange membrane” published in J. Memb. Sci. 257, 340, (2009) by Lacaze et al. This paper reported the preparation of AEM by radiochemical grafting of poly(4-vinylpyridine) chains on polymeric matrices. The AEM prepared by this process also avoid the use of CME.